Artificial line



Nov. 8,1927; 1,647,985

W. DEUTSCHMANN ARTIFICIAL LINE:

Filed Nov. 27. 1925 Patented` Nov. 8, 1927.

linarrlzo STATES PATENToFFlci-z.

WALTER DEUTSCHMANN, 0F BERLIN, GERMANY, ASSIGNOR TO SIEMENS VizfiEAIiSKE AKTIENGESELLSCHAFT, 0F SIEMENSSTADT, NEAR BERLIN, GERMANY, A COM- -,RANY 0F GERMANY.

ARTIFICIAL LINE.

Application led November 27, 1925, Serial No. 71,739, and in GermanyMay-22, 1924.

This yinvention relates to artificial lines for balancing loaded telephone lines.

en artificial lines are employed in connection with two-element. two-way repeaters for balancing the physical lines, the frequency range in which amplification may take place is definitely restricted in order to simplify the simulation of. the line impedance by the artificial line. It then remains necessary only to accurately simulate the impedances of the lines to be connected within this frequency range.

The invention aims to create a good` simulation of loaded lines in a simple Way, up to frequencies of about 0.8 to 0.9 of thecutolf frequency of the loaded line.

According to the invention, the balancing impedance consists of a network constructed so asto conform to a line section, its cutoff frequency is higher than that of the line to be simulated with equal or approximately equal iterative impedance and closed by means of an ohmic resistance. The invention can be more readily understood by reference to the following detailed description in connection with the drawing .in which? Fig. 1 shows the frequency-impedance characteristics of a loaded line and a balancing :net-work having the same cut-off frequency,

Fig. 2 shows the frequency-impedance characteristics of a loaded line and a network designed according to this invention, and Fig.

3 one formof this invention.

In Fig. 1 of the drawing, the frequency impedance characteristic of a network having the same constants as asection of the line closed by means of an ohmic resistance and its iterative impedance that by decreasing the vThe curve is plotted according to the formula derived from-Kirchhos Law:

It is plotted in Fig. 1 as shown by the dashed curve. It is obvious that the paths of the curves differ especially at the higher frequencies.

The invention is based on the consideration roduct LC in the simulating section, the requency at which the impedance of the balancing network is a maximum increases, and a more -eXact simulation of the line impedance in the important frequency range may be obtained.

The ratio must naturally be kept approximately constant, that is to say, it must be kept equal to that of the original line. Fig. 2 shows the improved balance obtained by use of a mesh according to Fig. 3, in which the product LC is equal to 0.7 of this product in the case of the line to be simulated, or expressed in another way, whose cutoffv frequency is 1.2 times as great as the cut-off f frequency of the line. Corresponding to Fig. 1, the dotted line represents the impedance characteristic of the line to be simulated, and the continuous line represents the impedance characteristic of the simulating network. Fig. 2 shows that up l to frequency of w=14000, the simulation and of the imaginary components likewise do not variable supplementary condensers to the line and the simulating network and te,

`make the final resistance deviate from according to necessity.

Fig. 3 illustrates the connection of the simulating network.

What is claimed is:

1. An artificial line for simulating the impedance of a long loaded line comprising a section having shunt capacity and series inductance so proportioned that said section has an iterative impedance substantially equal to that of the loaded line and a cut-off 1925 frequency substantially higher than that of the line, and a terminating resistance sub# stantially equal to the iterative impedance of the section.

2.` An artificial line according to claim 1 in which said inductance and capacity are so proportioned that the cut-off frequency of said section is substantially 1.2 times the cutoff frequency of the line.

3. An artificial net work for simulating the impedance of a long loaded line having an iterative impedance Z and a cut-off frequency f comprising a 1r type section l^ g a series inductance L and shunt cond users each of capacity 2C of such value that the is substantially equal to Z and that 1T-C is substantially equal to 1.2i, and a resistance havin a value substantially equal to Z connectec in shunt to one of said condensers.

In witness whereof, I hereunto subscribe my name this 26th day of October, A. D.,

WALTER DEUTSCHMANN. 

